As you can see, Stephen, I'm back. I have found that reference to the Identical twins discordant for sexual orientation.
GSA: Interrogating the Epigenetics of Sexual Orientation June 14, 2010 Also at GSA's Genetics 2010: Model Organisms to Human Biology conference in Boston this week, Eric Vilain of the University of California, Los Angeles, spoke about his work interrogating the most sexually dimorphic behavioral trait in humans - sexual orientation - via methylation patterns, or what he calls "epigaynomics." He and his team recruited 34 monozygotic twin pairs discordant for sexual orientation and interrogated 28,000 CpG loci on an Illumina platform. They found the methylation profile between gay and straight individuals to be "utterly similar" - the maximum difference between twins discordant for sexual orientation was only about 4 percent. What they did find, however, were distinguishable methylation patterns with age - three genes, they determined, explain nearly 70 percent of age-related variance. Vilain said that it's possible their CpG analysis wasn't exhaustive enough to capture epigenetic variation or that their inference of environmental effects was too limited. Ultimately, their results show "no detectable significant epigenetic [patterns] between monozygotic twin pairs discordant for sexual orientation." I still think epigenetics is the best bet here and while they didn't find it, they acknowledge that they can't completely rule it out. You said that the environments were the same but environments are never exactly the same. It could be as simple as an infection one had the other didn't or something prenatal. Ron http://www.childrenshospital.org/dream/summer10/different.html Interesting case. The possible cause of the discordance isn't mentioned, and there seems little room for either nature or nurture to vary: same genes, same environment. So how can this be? I know of one other example of striking discordance between MZ twins. In that case, one of the pair of female twins developed Duchenne muscular distrophy, a crippling disorder; the other twin became a skilled gymnast. It was explained as a result of an unusual pattern of X-inactivation of the X-chromosome. Since in this case both children are genetically male, a simlar explanation won't work here. Burn, J. et al (1986). Duchenne muscular dystrophy in one of monozygotic twin girls. J Med Genet 1986;23:494-500 Stephen -------------------------------------------- Stephen L. Black, Ph.D. Professor of Psychology, Emeritus Bishop's University e-mail: sblack at ubishops.ca 2600 College St. Sherbrooke QC J1M 1Z7 Canada ----------------------------------------------------------------------- --- --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=3506 or send a blank email to leave-3506-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
